\subsection{key - value 定义}
\begin{itemize}
    \item 使用 keyname/.style  定义key - value 值
    \item 使用 keyname/.append style 追加value
    \item 使用 keyname/.prefix style 插入value
\end{itemize}
\begin{tikzpicture}[point offset/.style 2 args={xshift=#1, yshift=#2}]
    \draw (0,0) grid (3, 2);
    \filldraw[color=red] ([point offset={1cm}{2cm}]0,0) circle (5pt);
\end{tikzpicture}

\subsection{node 坐标系}
\begin{tikzpicture}
    \node(shape) at (0, 2) [draw]{|class Shape|};
    \node(rect) at (-2, 0) [draw]{|class Rectangle|};
    \node(circle) at (2, 0) [draw]{|class Circle|};
    \node(ellipse) at (6, 0) [draw]{|class Ellipse|};

    \draw (node cs:name=circle, anchor=north) |- (0, 1);
    \draw (node cs:name=ellipse, anchor=north) |- (0, 1);
    %% usetikzlibrary{arrows.meta}
    \draw[arrows=-{Triangle[angle=60:3mm, open]}] (node cs:name=rect, anchor=north) |- (0,1)
      -| (node cs:name=shape, anchor=south);

\end{tikzpicture}
